Conventionally, many positioning devices for receiving positioning signals from GNSS satellites and performing a positioning have been put into practical use and used for various kinds of mobile terminals.
With such positioning devices, estimation calculations of positions or relative speeds of the own device are performed by substituting a pseudorange and carrier phases (delta ranges) that are observed using the positioning signals into track filters. Further, as the track filters, many Kalman filters such as the one disclosed in Nonpatent Document 1 have been used conventionally.
To such a conventional Kalman filter, a covariance matrix is given as a parameter to influence an estimation accuracy of the filter. Specifically, if it is a track filter for estimately calculating a pseudorange and a relative speed simultaneously, an error covariance matrix having an error variance of the pseudorange and an error variance of a relative positioning is given thereto.
Conventionally, the error variance of the pseudorange and the error variance of the relative positioning have simply been given with steady values or determined only by a C/No.
Further, Patent Document 1 discloses a positioning method of detecting multipath based on a difference value between an observed pseudorange and an estimated pseudorange so as not to use a reception signal (positioning signal) with a great error.
Further, Patent Document 2 discloses a positioning method of determining a reception environment based on a signal intensity, and correcting an error covariance of a Kalman filter according to the reception environment. In this method, the reception environment is determined in a stepwise manner, a correcting value is set for each step, and the original error covariance is corrected by the correcting value.